Common rail fuel systems typically employ multiple injectors connected to a common rail or manifold that is provided with high-pressure fuel. In order to efficiently accommodate different combinations of fuel injections at a variety of timings and injection amounts, the systems generally include a variable discharge pump in fluid communication with the common rail. One type of variable discharge pump is the cam driven, inlet or outlet metered pump.
A cam driven, inlet or outlet metered pump generally includes multiple plungers, each plunger being disposed within an individual pumping chamber. The plunger is connected to a lobed cam by way of a follower, such that, as the cam rotates, an associated lobe(s) causes the plunger to withdraw from the pumping chamber to draw fluid into the chamber, and then drives the plunger into the pumping chamber to displace fuel from the pumping chamber past an outlet check valve and into the common rail. The outlet check valve ensures that only fluid having a minimum threshold pressure passes into the common rail and that fluid from the common rail is inhibited from passing back into the pump.
Although effective, current outlet check valves used in pumping applications may be difficult and expensive to machine, and may have reduced durability. Thus, a new type of check valve may be useful for these applications.
An exemplary outlet check valve for use in a pumping application is disclosed in U.S. Pat. No. 6,244,295 (the '295 patent) issued to Bartussek et al. on Jun. 12, 2001. The '295 patent discloses an outlet check valve having a tubular valve housing in which a valve ball is received. The outlet check valve also has a perforated disk press-fitted between longitudinally-extending guide ribs and a circumferential wall of the valve housing. A helical compression spring is braced against the perforated disc and presses the valve ball against a valve seat. A collar is included on the perforated disc for centering the spring. The valve housing is made separate from the perforated disc.
During operation, the outlet check valve of the '295 patent allows fluid displaced by a pump piston to pass through the valve in a single direction. Specifically, as fluid comes into contact with the valve ball, it pushes the valve ball away from the seat and against the bias of the spring to compress the spring. As the valve ball moves away from the seat, the fluid is allowed to pass around the ball through an axial hole in the perforated disc to exit the check valve.
Although perhaps simple and inexpensive to fabricate, the outlet check valve of the '295 patent may still be problematic. Specifically, because the perforated disc is press fitted into the valve housing, it may be inhibited from moving during operation of the check valve. And, as the perforated disc functions as a spring guide, the fixed nature of the guide may provide opportunities for misalignment and binding of the spring and valve ball.
The disclosed check valve is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.